Description: The Mass Spectrometry Center is equipped with (1) a VG/Micromass 7070E double focusing mass spectrometer with electron ionization (EI), chemical ionization (CI), and fast atom bombardment (FAB) ionization modes that may be operated in either the positive-ion or the negative-ion mode, equipped with a continuous-flow FAB probe, (2) a VG/Micromass gas isotope ratio mass spectrometer, (3,4) two Hewlett-Packard MSD capillary gas chromatograph-mass spectrometer systems with low resolution, electron ionization, positive-ion mode GC/MS operation only, and (5) a Hewlett-Packard 5989A MS engine capable of electron ionization and chemical ionization, equipped with an HP 5890 gas chromatograph and auto injection. The laboratory also performs organic synthesis of stable-isotope-labeled and other specialty chemicals. About 10 percent of the activity of the MS Center serves this MRRD program.